1. Field of the Invention
The present invention relates to an iris recognition system and method and, more particularly, to an iris recognition system and method using a multifocus image sequence that can reduce the time required for obtaining eye images since the eye images of various levels are obtained in sequence from an image obtaining apparatus by changing focuses at regular time intervals within a predetermined distance when receiving an eye image of a user. Moreover, the iris recognition system and method using a multifocus image sequence of the present invention can recognize not only well focused images but also poorly focused images since eye images that can well reflect focus changes are selected and utilized using a fuzzy entropy.
2. Description of Related Art
In general, in order to identify users based on the users' biological characteristics, fingerprints, faces, irises, palm prints and the like have been utilized. It has been known that the irises provide an excellent personal identification performance and thereby show a security performance higher than the other biological information.
A conventional iris recognition system is designed to obtain only high quality images in a process of receiving users' eye images from a camera to enhance the personal identification performance and the security performance.
However, the conventional iris recognition system has disadvantages in that the time for adjusting a focus to obtain a well focused iris image is required too much when inputting an eye image and a user is forced to meet his or her eye in an accurate position through voice messages, thus causing considerable inconvenience to the user.
Moreover, the conventional iris recognition system has further disadvantages in that, if an eye image that is not well focused by the user's movement is input, it cannot correctly identify the user. In such a case, the user should have his/her eye image photographed again and wait until an recognition process is finished, thus increasing the total processing time of the iris recognition system, deteriorating the recognition rate and increasing the inconvenience.
Furthermore, the conventional iris recognition technique utilizes an iris area existing between pupil and sclera and uses a method for extracting an area between an inner boundary corresponding to a boundary of the pupil and the iris and an outer boundary of the pupil and the sclera to extract such an iris area between the pupil and the sclera.
The conventional method for extracting such an iris area has a disadvantage in that, due to a difference in the color tone between the pupil and the iris, the inner boundary can be easily located, whereas, the outer boundary is hardly found out.
In addition, the iris area extracted in such a manner includes a considerable amount of an unnecessary area where iris patterns barely appear as well as an area including various iris patterns that are useful for the personal identification. Accordingly, such an unnecessary area may have a bad influence in forming an iris code or an iris feature vector that is used in the recognition process.
Furthermore, in the field of the conventional iris recognition technique, a method for forming a binary iris code using Gabor transform or wavelet transform, or a method for forming a feature vector using a statistic value has been mainly used to extract the features of irises.
In the case where the Gabor transform or the wavelet transform is used for generating a binary iris code, if a captured image is seriously blurred, the recognition may be unavailable. Moreover, a feature vector formed using a statistic value of a subband having only high-frequency components among the subbands multi-divided by conventional Harr wavelet transform and Daubechies wavelet transform is sensitive to noise images and further has a low efficiency from a practical point of view in forming a low dimensional feature vector.
Accordingly, it is necessary to provide a technique that can efficiently process, store, transmit and search the pattern information that is less affected by an iris image quality in an iris recognition system.